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vacuum line under dash

Started by rumb, 29 September 2016, 02:28 PM

rumb

Can anyone identify this yellow line with the check valve on the end that doesnt connect to anything? It's right behind the instrument cluster.  also note the rubber hose just above/behind it in the picture. do these go together?  the check valve end looks bigger than the hose ID.

on chassis #1952

'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

tcj

The yellow line belongs to your central locking system. This one should probably end next to the
fuse box at a blue check valve in the engine compartment. There should be no check valve behind the
instrument cluster.
Someone has tried to fix some of the usual problems with this additional check valve.

Thomas
112.021
113.042
116.028
116.036

rumb

Thanks,

the black hose pictured does indeed connect to the yellow one you mention by the fuse box. I have never tried to use the vacuum locks on this car yet. I bet they didnt work....


I will re-attach and remove the check valve. Do you happen to know where the other end of the big yellow one is?


New strange thing:

In the picture this is the bundle that runs just in front of driver front door down by floorboards.

If I touch or push on the gray with yellow stripe there is some relay under the dash that clicks. Will try to figure out which relay tomorrow.

what is the gray/yellow one for?  how could that possibly make a relay click?  This is with key off.


oh, looks like the picture is sideways, the right side is down.



'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

ptashek

#3
Both of my cars got one of these. Same part, same placement, and no indication in the EPC for either VIN. I can't remember what it was for though, but the only thing that's around there is the HVAC system. I doubt three different cars were botch-repaired in the exact same way, but nothing's impossible.

The part number for this valve is A1238000078 (black/white) for late chassis, or A1168000378 (black/blue) for early ones.
Edit: At least two of these are also under the hood (or four, on cars with headlight vacuum-adjustment).
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

rumb

was/are yours disconnected - like mine - or connected?

I have the 2 check valves by the fuse box. blue/black ones.

Quote from: ptashek on 29 September 2016, 03:47 PM
Both of my cars got one of these. Same part, same placement, and no indication in the EPC for either VIN. I can't remember what it was for though, but the only thing that's around there is the HVAC system. I doubt three different cars were botch-repaired in the exact same way, but nothing's impossible.

The part number for this valve is A1238000078 (black/white) for late chassis, or A1168000378 (black/blue) for early ones.
Two of these are also under the hood (or four, on cars with headlight vacuum-adjustment).
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

ptashek

Quote from: rumb on 29 September 2016, 03:52 PM
was/are yours disconnected - like mine - or connected?
I have the 2 check valves by the fuse box. blue/black ones.

Definitely connected on both cars.
And I've found in the service manual what it's for! (page reference: 80.3-260/4 F2 "Leaking locking and unlocking circuit")

Quote"Since August 1976, the yellow suction line under instrument panel is additionally provided with a check valve (white-black). Never use the additional check valve at any other point of the vacuum system, since the correct function of the system is then no longer assured."

Mystery solved :)
Also, according to the manual, the grey-yellow line is a "suction line line from distributor to vacuum supply tank".
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

rumb

#6
Found the culprit on the relay clicking.  I knew that a  vacuum line was not really going to cause a relay to click, so I started looking at the wires.  Pulled out the 2 button switches on the door jamb and found this one that had one side unplugged and it had a short wire spliced onto it with a bare wire end that was shorting out when I wiggled the vac lines.

Where do people come up with fixes like this?  I could not find anything that the spliced blue wire could have been connected to.

What does this switch and relay control?  inside lights or ? 
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

ptashek

Was your car ever fitted with an alarm? That could be the trigger wire for an alarm relay.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

rumb

'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

wbrian63

Quote from: rumb on 30 September 2016, 06:05 PM
Found the culprit on the relay clicking.  I knew that a  vacuum line was not really going to cause a relay to click, so I started looking at the wires.  Pulled out the 2 button switches on the door jamb and found this one that had one side unplugged and it had a short wire spliced onto it with a bare wire end that was shorting out when I wiggled the vac lines.

Where do people come up with fixes like this?  I could not find anything that the spliced blue wire could have been connected to.

What does this switch and relay control?  inside lights or ?
I've read somewhere that "some cars" with two pin switches in the driver's door use one of the pins for the interior lights, and the 2nd one to allow for power window operation with the key off...
W. Brian Fogarty

'12 S550 (W221)
'76 450SEL 6.9 Euro #521
'02 S55 AMG (W220) - sold
'76 450SEL 6.9 Euro #1164 - parted out

"Bond reflected that good Americans were fine people, and most of them seemed to come from Texas..." Casino Royale, Chapter V

rumb

'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio

rumb


I've read somewhere that "some cars" with two pin switches in the driver's door use one of the pins for the interior lights, and the 2nd one to allow for power window operation with the key off...
[/quote]


Traced to window relay, and yes I can operate windows with the ignition turned off.

'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,
'16 AMG GTS
'21 E450 Cabrio